Milling machine control system

ABSTRACT

A milling machine includes a primary drum drive assembly for its milling drum, and a ground-engaging drive assembly for driving the milling machine along a roadway. A lifting column is attached between the frame and the ground-engaging drive assembly. The lifting column includes a linear actuator which can raise and lower the frame of the machine with respect to the roadway. A sensor mounted to the lifting column is adapted to determine if the lifting column is not supporting at least a predetermined portion of the weight of the milling machine. A controller is operatively attached to the drive assemblies and to the sensor, and is adapted to receive from the sensor a signal indicating that the lifting column is not supporting the predetermined portion of the weight of the milling machine. Upon receipt of such signal, the controller will automatically control certain machine functions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/596,271, which was filed on Oct. 8, 2019, which itself is acontinuation-in-part of U.S. patent application Ser. No. 16/139,273 (nowabandoned), which was filed on Sep. 24, 2018 and claims the benefit ofU.S. Provisional Patent Application No. 62/582,715, which was filed onNov. 7, 2017.

FIELD OF THE INVENTION

This invention relates generally to a system for automatically takingaction to control a milling machine during the performance of a millingoperation when the system anticipates that the machine drive assemblymay lose traction and/or that the milling drum may experience akick-back event. More particularly, the system allows for slowing orstopping a drive assembly of a milling machine during the performance ofa milling operation when the system anticipates that the drive assemblymay lose traction, and/or for stopping the rotation of the milling drumwhen the system anticipates that the milling drum may experience akick-back event. The invention comprises a system for anticipating theseadverse circumstances and for automatically taking control of certainmachine operations when a lifting column to which a drive assembly isattached is not providing adequate support.

BACKGROUND AND DESCRIPTION OF THE PRIOR ART

This discussion of the Background of the Invention is intended to aidthe reader in understanding the invention described herein, and shouldnot be considered to be an exhaustive discussion of the prior art.Furthermore, the observations described herein relating to technicalproblems addressed by the inventors should not be read to indicate orimply that knowledge of such problems existed in the prior art.

Roadway repair is often accomplished by overlaying the existing pavement(whether of concrete or asphalt paving material) with a new layer (oftencalled a leveling course) of concrete or asphalt paving material.Without prior surface treatment, however, this method of repairgenerally results in the application of insufficient quantities ofpaving material in the rutted, pot-holed or otherwise damaged areas,because the overlay will be applied at the same rate per unit of roadwaywidth in damaged areas (which have a greater depth to be filled acrossthe width) as in the undamaged areas. The resulting reduced thickness inthe overlay of the previously damaged areas will lead to renewed ruttingor other wear damage in the new pavement in relatively short order.However, by milling the surface of the damaged pavement to a uniformsurface elevation below the level of the damage, the addition of newpavement will produce a road surface having a consistent elevationacross the entire width of the roadway. This repaving technique can beused to return the elevation of a damaged roadway to its originalpre-damaged elevation, whereas the placement of a leveling course atopdamaged but un-milled pavement will tend to raise the surface of theroadway or some portion thereof above its original elevation. Roadwayrepair without milling can require the raising of road shoulders,guardrails and manhole covers and the adjustment of overpass clearances,all of which are unnecessary if a proper milling technique is employed.A use of milling prior to repaving can also permit ready establishmentof the proper road grade and slope, and thereby avoid drainage andsafety problems. Furthermore, milling typically provides a rough surfacethat readily accepts and bonds with the new asphalt or other pavementoverlay. Finally, milling can provide raw material that can be reclaimedfor use in the production of new paving materials.

A milling machine typically comprises a wheel-driven or track-drivenvehicle that includes a milling drum having a plurality of cutting teethdisposed around its periphery. The milling drum is mounted for rotationabout a substantially-horizontal axis within a drum housing on the frameof the machine. Steerable wheel-drive or track-drive assembliestypically operated by hydraulic motors are provided to drive the machinein a milling direction and to steer it along a desired milling path. Thedrive assemblies are attached to lifting columns that include internallinear actuators which can be activated to raise and lower the frame ofthe machine with respect to the roadway surface. Wheel-driven machinesinclude four ground-engaging wheel-drive assemblies, one at the leftfront, one at the right front, one at the left rear and one at the rightrear. Track-driven machines include three or four ground-engagingtrack-drive assemblies including one at the left front and one at theright front. Some such machines will also include a third track-driveassembly at the left rear and a fourth at the right rear; however, sometrack-drive machines will have only a single, center-mounted reartrack-drive assembly. Each of the ground-engaging drive assemblies isoperatively attached to or comprises a drive control system and isadapted to provide a driving force to drive the milling machine alongthe roadway surface. The drive control system typically comprises ahydraulic motor and a gearbox with an integrated friction brake. Thesehydraulic motors for the ground-engaging drive assemblies are part of ahydraulic circuit that includes a hydraulic fluid pump.

Since the milling drum is mounted for rotation in a housing on the frameof the machine, raising the frame on the lifting columns can raise themilling drum out of contact with the roadway surface, and lowering theframe on the lifting columns can lower the milling drum into contactwith the road surface so as to make a cut of the desired depth. Themilling drum is rotated by a primary drum drive assembly typicallycomprising a drive belt driven by a diesel engine, which drive beltengages a drivetrain comprising a sheave on an input drive shaft for themilling drum. A gear box is typically located between the sheave and themilling drum and includes a gear train and an output drive shaft onwhich the milling drum is rotated. The gear box thus allows for rotationof the output drive shaft for the milling drum at a speed and torquethat is different from that of the input drive shaft. A milling machinemay include a conveyor system that is designed to carry the milledmaterial that has been cut from the roadway by the rotating milling drumto a location in front of, to the rear of, or beside the machine fordeposit into a truck for removal from the milling site. Power foroperation of the hydraulic motors that are typically employed to operatethe conveyors and the drive assemblies is usually provided by the dieselengine.

A road stabilizer is a type of milling machine that does not include aconveyor system which is designed to carry the milled material that hasbeen cut from the roadway by the rotating milling drum away from themachine. Instead, the milling drum of a road stabilizer is generallyemployed to mill or pulverized an existing road bed or roadway to agreater depth than does a milling machine prior to repaving (usuallycalled reclaiming) or prior to initial paving (usually calledstabilizing), and it leaves the pulverized material in place. Thepulverized material left behind is usually compacted and covered withone or more additional layers of crushed aggregate material beforepaving.

Cold in-place recycling (“CIR”) machines can be used to repair damage toa roadway in a single pass, while reusing essentially all of theexisting asphalt paving material. In the CIR process, damaged layers ofasphalt pavement are removed. The removed material is processed andreplaced on the roadway and then compacted. If a roadway has goodstructural strength, CIR can be an effective treatment for all types ofcracking, ruts and holes in asphalt pavement. CIR can be used to repairasphalt roadways damaged by fatigue (alligator) cracking, bleeding (ofexcess asphalt cement), block cracking, corrugation and shoving, jointreflective cracking, longitudinal cracking, patching, polishedaggregate, potholes, raveling, rutting, slippage cracking, stripping andtransverse (thermal) cracking. CIR can almost always be used when thereis no damage to the base of the roadway. Generally, CIR is only half asexpensive as a new pavement overlay while providing approximately 80% ofthe strength of new pavement. CIR can be carried out by a CIR machinecomprising a milling machine or a road stabilizer machine that has beenmodified by mounting an additive spray bar in the milling drum housingto inject an asphalt emulsion or foamed asphalt cement additive into themilling drum housing. The asphalt emulsion or foamed asphalt cementadditive is then thoroughly blended with the milled material by themilling drum and can be left in a windrow or fed by the CIR machine'sdischarge conveyor directly into an asphalt paving machine. When a CIRprocess is carried out by a modified milling machine or road stabilizer,the additive material is supplied from a separate additive supply tanktruck that is coupled to the modified milling machine or road stabilizermachine. The additive material is drawn directly from the tank on theadditive supply truck and metered through an additive flow system thatis mounted on the milling machine to the spray bar in the milling drumhousing. Because the milling drums and ground-engaging drive assembliesof a milling machine and a road stabilizer (including those modified toperform a CIR process) operate in the same way for purposes of thisinvention, the term “milling machine” will be used hereinafter as ageneric term that describes all of these machines.

During the operation of a milling machine, the lifting columns areemployed to set the depth of the cut of the milling drum, and themachine operator advances the milling machine at a rate that permits themilling drum to make the desired cut in the roadway. However,circumstances may arise in which the milling drum encounters increaseddensity material in the roadway during a milling operation, causing themachine to rise up out of the cut. In such circumstances, a millingmachine having an automatic grade control system will attempt tocompensate for the rise in the milling drum by lowering the frame on thelifting columns. This will cause an undesirable portion of the weight ofthe milling machine to be supported by the milling drum instead of thelifting columns, and may result in a loss of steering or braking controlbecause of insufficient contact between the drive assemblies on thelifting columns and the roadway. This occurrence is dangerous for themachine operator and may also lead to damage of the milling machine. Forexample, if the reaction forces exerted by the roadway surface on themilling drum exceed the opposing forces applied to the milling drum bythe lifting columns, the machine may lurch backward or forward dependingon the direction of rotation of the milling drum. If the milling machineis operating in a down cut mode (i.e., with the milling drum rotating soas to cut downwardly in the direction of travel of the machine), themachine may lurch forward, whereas if the machine is operating in an upcut mode (i.e., with the milling drum rotating so as to cut upwardly inthe direction of travel of the machine), the machine may lurchbackwards. The terms “kick-back”, “kick-back event”, and similar termswill be used hereinafter to describe the lurching, either forward orbackward, that occurs or may occur when the milling drum encountersconditions that cause an undesirable portion of the weight of themilling machine to be supported by the milling drum instead of thelifting columns.

Furthermore, as mentioned above, if circumstances arise in which anundesirable portion of the weight of the milling machine to be supportedby the milling drum instead of the lifting columns, the milling machinemay experience a loss of steering or braking control because ofinsufficient contact between the ground-engaging drive assemblies on thelifting columns and the roadway.

U.S. Pat. No. 5,318,378 describes a milling machine having a kick-backcontrol system. In one embodiment, the kick-back control system includesa pressure sensor that is in fluid communication with the pressurechamber of one of the lifting columns. In this embodiment, the pressuresensor will communicate with a controller that can direct pressurizedhydraulic fluid to the upper or lower pressure chamber of the liftingcolumn to raise or lower the frame of the machine to maintain a desiredelevation of the milling drum. However, the inventors have observed thatsuch a system cannot anticipate a kick-back event, and furthermore, thatit is subject to providing false signals to the controller due toadjustments that may be made by the grade control system. In a secondembodiment, the kick-back control system includes a load cell or straingauge that is attached to the inner leg tube of a lifting column. Thisload cell or strain gauge is adapted to sense the compressive force,transmitted through the inner leg tube, which is imparted to the frameof the milling machine by the kick-back event. The load cell or straingauge is operatively connected to a controller that may be activated toraise the frame on the affected lifting column and/or to stop therotation of the milling drum. However, a disadvantage of this embodimentof the kick-back control system, like that of the first embodiment, isthat it can only react after a kick-back event has occurred. Anotherdisadvantage of this kick-back control system is that location of theload cell or strain gauge on the inner leg tube of a lifting columnplaces the load cell or strain gauge on a component (i.e., the inner legtube) that moves with respect to the frame during normal operation ofthe milling machine. This subjects the load cell or strain gauge tobending moments caused by the imposition of directional forces due tonormal forward motion or steering of the drive assembly. These bendingmoments could affect the ability of the load cell or strain gauge toaccurately sense the compressive forces caused by a kick-back event andcould lead to a failure to react to a kick-back event, or to a kick-backreaction when no kick-back event has occurred.

U.S. Pat. No. 5,879,056 describes a milling machine having a separatewheel assembly that is adapted to rotate in a forward direction when themachine travels in a forward direction and in a backward direction whenthe machine travels in the opposite direction. The assembly alsoincludes an electronic sensor that detects when the wheel travels in thebackward direction and signals a controller to disable the milling drumwhen the wheel travels in the backward direction by a predetermineddistance.

U.S. Pat. Nos. 8,128,177, 8,292,371 and 8,632,132 describe millingmachines that include strain gauges that are mounted on opposite sidewalls of the milling drum housing and are adapted to measure thereaction force of the roadway surface on the milling drum that istransmitted through the drum housing. These strain gauges transmitsignals to a controller when the reaction force has exceeded apredetermined level, and the controller then reduces the power to themachine drive assemblies and/or reduces the rate at which the millingdrum is lowered into contact with the roadway surface.

Notes on Construction

The use of the terms “a”, “an”, “the” and similar terms in the contextof describing the invention are to be construed to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising”, “having”, “including”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The terms“substantially”, “generally” and other words of degree are relativemodifiers intended to indicate permissible variation from thecharacteristic so modified. The use of such terms in describing aphysical or functional characteristic of the invention is not intendedto limit such characteristic to the absolute value which the termmodifies, but rather to provide an approximation of the value of suchphysical or functional characteristic.

Terms concerning attachments, coupling and the like, such as “attached”,“coupled”, “connected” and “interconnected”, refer to a relationshipwherein structures are secured or attached to one another eitherdirectly or indirectly through intervening structures, as well as bothmoveable and rigid attachments or relationships, unless specified hereinor clearly indicated by context. The terms “operatively connected” and“operatively attached” describe such an attachment, coupling orconnection that allows the pertinent structures to operate as intendedby virtue of that relationship.

The use of any and all examples or exemplary language (e.g., “such as”and “preferably”) herein is intended merely to better illuminate theinvention and the preferred embodiment thereof, and not to place alimitation on the scope of the invention. Nothing in the specificationshould be construed as indicating any element as essential to thepractice of the invention unless so stated with specificity. Severalterms are specifically defined herein. These terms are to be given theirbroadest reasonable construction consistent with such definitions, asfollows:

The term “milling machine” refers to a vehicle having a milling drumthat is adapted to be rotated so as to cut into the surface on which thevehicle is operated, and includes machines that may be called millingmachines, cold planers, road stabilizers or reclaiming machines.

The term “milling direction” refers to the primary direction of travelof a milling machine as it operates on a roadway.

The terms “front”, “forward” and similar terms, when used with respectto a milling machine or a component of such a machine, refer to arelative location or direction towards the leading end of the millingmachine as it travels in the milling direction.

The terms “rear”, “behind” and similar terms, when used with respect toa milling machine or a component of such a machine, refer to a relativelocation or direction towards the trailing end of the milling machine asit travels in the milling direction.

The terms “upper”, “top”, “above” and similar terms, when used inreference to a relative position or direction on or with respect to amilling machine, or a component or portion of such a machine, refer to arelative position or direction that is farther away from the surface onwhich the milling machine is placed for operation.

The terms “lower”, “bottom”, “below” and similar terms, when used inreference to a relative position or direction on or with respect to amilling machine, or a component or portion of such a machine, refer to arelative position or direction that is nearer to the surface on whichthe milling machine is placed for operation.

The term “load cell sensor” refers to a transducer or sensor that isused to generate an electrical signal having a magnitude that isdirectly proportional to a force being measured. A strain gauge loadcell sensor generates a signal that corresponds to the deformation orstrain perceived by the load cell sensor, as a change in electricalresistance, which is a measure of the applied force.

The term “linear actuator” refers to an electric, pneumatic, hydraulic,electro-hydraulic or mechanical device that generates force which isdirected in a straight line. One common example of a “linear actuator”is a hydraulic actuator which includes a cylinder, a piston within thecylinder, and a rod attached to the piston. By increasing the pressurewithin the cylinder on one side of the piston (over that on the oppositeside of the piston), the rod will extend from the cylinder or retractinto the cylinder.

SUMMARY OF THE INVENTION

The invention comprises a milling machine having a frame to which amilling drum is mounted, and a primary drum drive assembly for drivingthe milling drum. The milling machine also includes a ground-engagingdrive assembly for driving the milling machine along a roadway and adrive control system for the ground-engaging drive assembly. A liftingcolumn is attached between the frame of the milling machine and theground-engaging drive assembly. The lifting column includes a linearactuator which can raise and lower the frame of the machine with respectto the roadway. A load cell sensor mounted to the lifting column isadapted to determine if the lifting column is not supporting at least apredetermined portion of the weight of the milling machine. The loadcell sensor is attached to a top bracket of the lifting column in such amanner that it does not rotate or otherwise move with respect to theframe of the milling machine as the lifting column or theground-engaging drive assembly is operated. Preferably, the load cellsensor is a pin-type load cell that is used to attach the upper end ofthe linear actuator to the outer leg tube of the lifting column. Acontroller is operatively attached to the primary drum drive assembly,to the drive control system for the ground-engaging drive assembly, andto the load cell sensor, and the controller is adapted to receive fromthe load cell sensor a signal indicating that the lifting column is notsupporting the predetermined portion of the weight of the millingmachine. Upon receipt of such signal, the controller will automaticallyinitiate control of certain machine functions in order to prevent akick-back event or a loss of control of the milling machine.

In order to facilitate an understanding of the invention, the preferredembodiments of the invention, as well as the best mode known by theinventors for carrying out the invention, is illustrated in thedrawings, and a detailed description thereof follows. It is notintended, however, that the invention be limited to the particularembodiments described or to use in connection with the apparatusillustrated herein. Therefore, the scope of the invention contemplatedby the inventors includes all equivalents of the subject matterdescribed herein, as well as various modifications and alternativeembodiments such as would ordinarily occur to one skilled in the art towhich the invention relates. The inventors expect skilled artisans toemploy such variations as seem to them appropriate, including thepractice of the invention otherwise than as specifically describedherein. In addition, any combination of the elements and components ofthe invention described herein in any possible variation is encompassedby the invention, unless otherwise indicated herein or clearly excludedby context.

BRIEF DESCRIPTION OF THE DRAWINGS

The presently preferred embodiment of the invention is illustrated inthe accompanying drawings, in which like reference numerals representlike parts throughout, and wherein:

FIG. 1 is a side view of a milling machine which includes the invention.

FIG. 2 is a top view of the milling machine shown in FIG. 1.

FIG. 3 is a front view of certain components of the primary drum driveassembly for the milling drum of the milling machine illustrated inFIGS. 1 and 2.

FIG. 4 is an enlarged view of the right rear lifting column andground-engaging drive assembly of the milling machine shown in FIGS. 1and 2, with a side panel removed to illustrate certain components of thelifting column.

FIG. 5 is a schematic view of certain components of the drive controlsystem for the ground engaging drive assemblies of the milling machineshown in FIG. 1.

FIG. 6 is an exploded view of the right rear lifting column shown inFIG. 4.

FIG. 7 is a side view of a portion of the lifting column shown in FIGS.4 and 6.

FIG. 8 is a sectional view through the portion of the lifting columnshown in FIG. 7, taken along the line 8-8 of FIG. 7.

FIG. 9 is a top view of the portion of the lifting column shown in FIG.7.

FIG. 10 is a perspective view of a preferred embodiment of a load cellsensor that is a part of the invention, showing a first embodiment of asensor mounting bracket that is adapted to be attached to the uppersurface of the top bracket of the outer leg tube of a lifting column.

FIG. 11 is a perspective view of a portion of a preferred embodiment ofa load cell sensor that is part of the invention, showing a secondembodiment of a sensor mounting bracket that is adapted to facilitatethe attachment by the load cell sensor of the upper end of the linearactuator to the outer leg tube of a lifting column.

FIG. 12 is a perspective view of a preferred embodiment of a load cellsensor that is a part of the invention, showing the second embodiment ofthe sensor mounting bracket that is adapted to be attached to the uppersurface of the top bracket of the outer leg tube of a lifting column.

FIG. 13 is a perspective view of a portion of a preferred embodiment ofa load cell sensor that is part of the invention, showing a thirdembodiment of a sensor mounting bracket that is adapted to facilitatethe attachment by the load cell sensor of the upper end of the linearactuator to the outer leg tube of a lifting column.

FIG. 14 is a perspective view of a preferred embodiment of a load cellsensor that is a part of the invention, showing the third embodiment ofthe sensor mounting bracket that is adapted to be attached to the uppersurface of the top bracket of the outer leg tube of a lifting column.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

This description of the preferred embodiments of the invention isintended to be read in connection with the accompanying drawings, whichare to be considered part of the entire written description of thisinvention. The drawing figures are not necessarily to scale, and certainfeatures of the invention may be shown exaggerated in scale or insomewhat schematic form in the interest of clarity and conciseness.

As shown in FIGS. 1 and 2, a milling machine that is equipped with apreferred embodiment of the invention is indicated generally at 20. Thismachine comprises a mobile vehicle having a frame 22 and a plurality ofground-engaging drive assemblies that are attached to lifting columns,including right front track drive assembly 24 which is attached tolifting column 26, a left front track drive assembly (not shown butsubstantially similar to right front track drive assembly 24), rightrear track drive assembly 28 which is attached to right rear liftingcolumn 30, and a left rear track drive assembly (not shown butsubstantially similar to right rear track drive assembly 28). As isknown to those having ordinary skill in the art, the milling machine mayinclude only a single center-mounted rear ground-engaging track driveassembly, or it may include four wheel-driven ground-engaging driveassemblies instead of track-driven ground-engaging assemblies.Preferably, at least the front ground-engaging drive assemblies aresteerable to provide precise directional control. Each of theground-engaging drive assemblies is operatively attached to or comprisesa drive control system and is adapted to provide a driving force todrive the milling machine along the roadway surface.

Milling machine 20 also includes a milling assembly comprising agenerally cylindrical milling drum 32 having a plurality of cuttingteeth (not shown) mounted around its periphery. The milling drum isrotated about a substantially-horizontal axis of rotation within drumhousing 33 on frame 22 by primary drum drive assembly 34. This primarydrum drive assembly includes drive belt 35 that is operatively attachedto and is driven by an engine drive shaft of diesel engine 36, as shownschematically in FIG. 3, on which engine drive sheave 37 is mounted.Drive belt 35 is also operatively attached to drum sheave 38 on an inputdrive shaft for milling drum 32. In other embodiments of the invention(not shown), the primary drum drive assembly comprises one or morehydraulic motors (not shown) and a drive belt that engages a sheave onan input shaft for the milling drum. Gear box 39 is located between drumsheave 38 and the milling drum (not shown in FIG. 3) in both the primarydrum drive assembly comprising a direct engine drive shown in thedrawings, and in a primary drum drive assembly that includes one or morehydraulic motors. Gear box 39 includes a gear train and an output driveshaft on which the milling drum is rotated. The gear box thus allows forrotation of the output drive shaft for the milling drum at a speed andtorque that is different from that of the input drive shaft. Primarydrum drive assembly 34 also includes a belt tensioning assemblyincluding tensioning sheave 40, which is pivotally mounted within theprimary drum drive assembly, and tensioning actuator 41 that isoperatively attached to the tensioning sheave. Tensioning actuator 41 isa linear actuator that may be employed to move tensioning sheave 40 inorder to increase or decrease the tension of drive belt 35. Milling drum32 is adapted for cutting a width of material from the surface in thepath of the machine as milling machine 20 travels in milling direction“M” (shown in FIG. 1), and for depositing the milled material on firstconveyor 42, which carries it to second conveyor 44 for discharge into atruck.

The drive control system for each ground-engaging drive assemblypreferably comprises a hydraulic motor, such as right rear hydraulicmotor 46 _(RR) (shown in FIG. 5) that is operatively attached to rightrear gearbox 48 _(RR) with an integrated friction brake (shown in FIGS.4 and 5). Similarly, left rear hydraulic motor 46 _(LR) (shown in FIG.5) is operatively attached to left rear gearbox 48 _(LR) with anintegrated friction brake, right front hydraulic motor 46 _(RF) isoperatively attached to right front gearbox 48 _(RF) with an integratedfriction brake, and left front hydraulic motor 46 _(LF) is operativelyattached to left front gearbox 48 _(LF) with an integrated frictionbrake. In this preferred embodiment of the invention, the hydraulicmotors for the ground-engaging drive assemblies are part of a hydrauliccircuit that includes a hydraulic fluid pump 50 and associated controlvalves known to those having ordinary skill in the art to which theinvention relates. Hydraulic fluid pump 50 is driven by diesel engine36, which is also part of the drive control system for theground-engaging drive assemblies. The drive control system may operatethe engine, the hydraulic fluid pump and/or the control valves toincrease or decrease the flow of hydraulic fluid to one or more of thehydraulic motors to increase or reduce the driving force provided by theassociated ground-engaging drive assembly or assemblies. The drivecontrol system may also apply the integrated friction brake on one ormore ground-engaging drive assemblies to decrease the driving forceprovided by the ground-engaging drive assembly or assemblies.

A linear actuator, such as linear actuator 51 shown in FIGS. 4, 6 and 8,is mounted within each of the lifting columns of the ground-engagingdrive assemblies and is adapted to move the frame of the milling machinevertically with respect to the ground-engaging drive assemblies. Thus,the linear actuators within the lifting columns are adapted to raise theframe of the milling machine and the milling drum with respect to theroadway surface, or to lower the frame and the milling drum with respectto the roadway surface.

Milling machine 20 is operated by an operator in operator's station 52which includes controller 53. Controller 53 may embody a singlemicroprocessor or multiple microprocessors that include components forcontrolling the invention, including primary drum drive assembly 34 forrotation of milling drum 32, and the drive control system for theground-engaging drive assemblies, as well as other operations of millingmachine 20 based on input from an operator of the milling machine and onsensed or other known operational parameters. Thus, for example,controller 53 is operatively connected to a throttle assembly 54 (shownschematically in FIG. 3) for diesel engine 36 and to a hydraulic clutchassembly 55 (also shown schematically in FIG. 3) for engine 36, and isadapted to control the speed and operation of the diesel engine.Controller 53 is also operatively connected to hydraulic motors 46_(RR), 46 _(LR), 46 _(RF), 46 _(LF), and the associated gear boxes andfriction brakes, hydraulic fluid pump 50, and to the valves forcontrolling the flow of hydraulic fluid in the hydraulic circuit to thevarious components within the circuit, such as linear actuators 51 inthe lifting columns, the actuators that control the movement of certaincomponents of machine 20 including conveyors 42 and 44, and the otherhydraulic motors in the hydraulic circuit.

Controller 53 is preferably programmed with information about thevarious relative positions, configurations and dimensions of the millingdrum with respect to the frame, and the lifting columns supporting theground-engaging drive assemblies, including the linear actuatorscontained within the lifting columns, so that controller 53 candetermine the specific adjustments in the elevations of the liftingcolumns that are required to maintain a desired cut depth. Controller 53includes or is associated with a memory, and it will preferably includea data input component such as a touch screen, a keyboard and/or aplurality of actuating buttons for receiving input from an operator ofthe milling machine. Controller 53 may also include a data outputcomponent such as a display screen, a secondary storage device, aprocessor and other components for running an application. Variouscircuits may be associated with and operatively connected to thecontroller, such as power supply circuitry and hydraulic circuitry.Numerous commercially available microprocessors can be configured toperform the functions of controller 53. It should be appreciated thatthe controller could readily be embodied in a general purpose computeror machine microprocessor capable of controlling numerous millingmachine functions.

FIGS. 4-14 illustrate a preferred embodiments of certain components ofan assembly for automatically stopping the rotation of milling drum 32if the controller determines that right rear lifting column 30 is notsupporting a predetermined portion of the weight of the milling machinethat is indicative of a kick-back event, or if the controller determinesthat one or more of the ground-engaging assemblies is not supporting apredetermined portion of the weight of the milling machine that would besufficient to produce a driving force of sufficient magnitude to preventslippage of the track on the roadway surface. Thus, as shown therein,right rear lifting column 30 comprises inner leg tube 56 having abracket 57 on its lower end to which ground-engaging track driveassembly 28 is attached. The upper end of outer leg tube 58 is fixed toframe 22 of milling machine 20, and inner leg tube 56 is disposed withinthe outer leg tube. Linear actuator 51 is disposed within the inner legtube, as best shown in FIGS. 6 and 8, and is attached at its upper endto the outer leg tube and at its lower end to the inner leg tube, sothat operation of linear actuator 51 will cause the outer leg tube tomove axially with respect to the inner leg tube, thereby moving frame 22with respect to ground-engaging track drive assembly 28. The upper endof linear actuator 51 extends through top bracket 59 of outer leg tube58 and includes a hole 60 (shown in FIG. 8) which is aligned with holesin pin supports 61 and 62 (only one of which, hole 63 in pin support 62is shown in FIG. 6) of top bracket 59. Load cell sensor 64 is preferablya pin-type load cell that is placed through the holes in pin supports 61and 62 of top bracket 59 and through hole 60 in the upper end of thelinear actuator in order to attach linear actuator 51 to outer leg tube58. By locating load cell sensor 64 in top bracket 59 on top of theground-engaging lifting column, the load cell sensor will not move withrespect to the frame of the machine as the lifting column or theassociated track drive assembly is operated. Consequently, the load cellsensor will only detect vertically directed forces and will not besubject to bending moments caused by the imposition of directionalforces due to normal forward motion or steering of the drive assembly.In this respect, the invention represents an improvement over the systemof U.S. Pat. No. 5,318,378.

As shown in FIGS. 4, 6, 7, 9, and 10-14, load cell sensor 64 ispreferably substantially cylindrical and has an axis “A” (shown in FIGS.10-14) that is oriented substantially perpendicular to long axis “L” oflifting column 30 (shown in FIG. 8), i.e., the axis along which outerleg tube 58 (and frame 22) moves with respect to inner leg tube 56. Loadcell sensor 64 is attached to and spaced from the upper surface 59 _(US)of top bracket 59 of outer leg tube 58 by means of a sensor mountingbracket. In the embodiment of the invention shown in FIGS. 6, 9 and 10,sensor mounting bracket 65 comprises a U-shaped bracket. One end of loadcell sensor 64 is integrally attached to the bend of U-shaped sensormounting bracket 65, as best shown in FIG. 10, and the legs 66 ofU-shaped sensor mounting bracket 65 serve to space the attached end ofload cell sensor 64 away from upper surface 59 _(US) of top bracket 59.Thus, U-shaped sensor mounting bracket 65 is adapted to position theload cell sensor out of contact with the top bracket 59 by apredetermined clearance and to prevent rotation of the load cell sensor.Similarly, in the embodiments of the invention illustrated in FIGS.11-14, one end of load cell sensor 64 is mounted atop sensor mountingbracket 67 or sensor mounting bracket 68 to space the attached end ofload cell sensor 64 away from the upper surface 59 _(US) of top bracket59. These alternative sensor mounting brackets are adapted to positionthe load cell sensor out of contact with the top bracket 59 by apredetermined clearance and to prevent rotation of the load cell sensor.

With any of the disclosed embodiments of the sensor mounting bracket,load cell sensor 64, as placed through the upper end of linear actuator51 and mounted on top bracket 59, is positioned to measure the load orstrain on rear lifting column 30. Because of this mountingconfiguration, load cell sensor 64 is mounted to lifting column 30 insuch a manner that it detects only forces that are directed along longaxis “L” of the lifting column. Load cell sensor 64 is operativelyattached to controller 53 and is adapted to send signals indicative ofthe load or strain on the lifting column to the controller. Controller53 is also operatively attached to the drive control system for eachground-engaging drive assembly, and is adapted to control the operationof the drive control systems for the ground-engaging drive assemblies,including by slowing or stopping the driving force provided by eachground-engaging drive assembly. Controller 53 is also operativelyattached to the primary drum drive assembly, and is adapted to controlthe primary drum drive assembly, including by stopping the rotation ofthe milling drum.

During normal operation of the milling machine, the linear actuatorswithin the lifting columns control the axial positions of the outer legtubes with respect to the inner leg tubes in order to properly locatethe milling drum with respect to the roadway surface. Thus, for example,linear actuator 51 within right rear lifting column 30 controls theaxial position of outer leg tube 58 with respect to inner leg tube 56.The weight of milling machine 20 is supported primarily by thecomponents of the vertical lifting columns including right rear liftingcolumn 30. By virtue of the mounting of load cell sensor 64 with respectto linear actuator 51 as shown in the drawings, the axial deformation ofload cell sensor 64, i.e. deformation along axis “A” shown in FIGS.10-14, is a function of the portion of the weight of the milling machinethat is supported by lifting column 30. Thus, load cell sensor 64 isadapted to transmit to controller 53 a continuous voltage signal thatvaries as the sensed axial deformation changes. If the signal from theload cell sensor falls below a predetermined value, controller 53 willinterpret this signal as indicating a decrease in the load on liftingcolumn 30 to which the load cell sensor is attached, and thus a decreasein the portion of the weight of milling machine 20 that is supported bythe lifting column. When controller 53 determines that lifting column 30is not supporting at least a predetermined portion of the weight of themilling machine that is anticipatory of a kick-back event, such as, forexample, about 1200 pounds, controller 53 will stop the operation of theprimary drum drive assembly to rotate milling drum 32, by disengagingthe hydraulic clutch assembly 55, or by other means in anticipation of,and in order to prevent, a kick-back event.

Although it is preferable that a load cell sensor be mounted to at leastone rear lifting column in order to anticipate a kick-back event, loadcell sensors may be mounted to all of the lifting columns, in order toanticipate when the drive assembly to which the lifting column isattached may lose traction. In such event, the predetermined portion ofthe weight of the milling machine that, if not supported, would indicatea loss of traction would depend on how much torque is applied to thetrack-drive assembly, the travel speed of the milling machine, the trackcontact area on the roadway surface, and other factors. In suchcircumstances, the controller may be provided with two differentpredetermined portions of the weight of the milling machine, the firstof which, if not supported, would be indicative of a kick-back event,and the second of which, if not supported, would be indicative of a lossof traction. If so, the controller would be adapted, when the signalreceived from the sensor indicates that the lifting column is notsupporting at least the first predetermined portion of the weight of themilling machine, to cause the primary drum drive assembly to stop therotation of the milling drum, and it would also be adapted, when thesignal received from the sensor indicates that the lifting column is notsupporting at least the second predetermined portion of the weight ofthe milling machine, to cause the drive control system to slow or stopthe driving force provided by the ground-engaging drive assembly.

The invention employs a load cell sensor such as sensor 64 that ismounted to a lifting column such as rear lifting column 30. The loadcell sensor is adapted to measure a load or strain on the liftingcolumn, and to transmit to the controller a signal indicative of theload or strain measured by the load cell sensor. In this embodiment ofthe invention, the controller is adapted to receive the signalindicative of the load or strain measured by the load cell sensor fromthe load cell sensor, and to stop the rotation of the milling drum whenthe signal received from the load cell sensor indicates that the liftingcolumn is no longer supporting at least the predetermined portion of theweight of the milling machine that is indicative of the imminence of akick-back event. In addition or in the alternative, the controller isadapted to cause the drive control system to slow or stop the drivingforce provided by a ground-engaging drive assembly when the signalreceived from the sensor mounted to the lifting column indicates thatthe lifting column is not supporting at least the predetermined portionof the weight of the milling machine.

The invention thus provides a simple system for automatically stoppingthe rotation of the milling drum, and/or for slowing or stopping thedriving force provided by a ground-engaging drive assembly, if thesystem determines that the milling drum is not being sufficientlysupported by a lifting column, thereby preventing a lurch backwards or alurch forwards of the milling machine, depending on the direction ofrotation of the milling drum, and/or a loss of control of the millingmachine.

Although this description contains many specifics, these should not beconstrued as limiting the scope of the invention but as merely providingan illustration of the presently preferred embodiments thereof, as wellas the best mode contemplated by the inventors of carrying out theinvention. The invention, as described herein, is susceptible to variousmodifications and adaptations as would be appreciated by those havingordinary skill in the art to which the invention relates.

What is claimed is:
 1. A milling machine for milling a roadway surface,said milling machine having a milling machine weight and furthercomprising: (a) a frame; (b) a milling assembly comprising: (i) a drumhousing that is attached to the frame; (ii) a milling drum that ismounted within the drum housing and adapted for rotation about asubstantially horizontal axis; (c) a ground-engaging drive assembly thatis operatively attached to a drive control system and is adapted toprovide a driving force to drive the milling machine along the roadwaysurface; (d) a lifting column that is attached at its upper end to theframe and at its lower end to the ground-engaging drive assembly, saidlifting column including: (i) an outer leg tube which is fixed to theframe and which has a top bracket with an upper surface; (ii) a linearactuator which can be operated to raise and lower the frame of themachine with respect to the roadway surface; (e) a load cell sensor thatis: (i) attached to the top bracket of the lifting column in such amanner that it does not rotate or otherwise move with respect to theframe as the lifting column or the ground-engaging drive assembly isoperated; (ii) adapted to determine if the lifting column is notsupporting at least a predetermined portion of the weight of the millingmachine; (iii) adapted to generate a signal indicating that the liftingcolumn is not supporting at least the predetermined portion of theweight of the milling machine; (f) a controller that is: (i) operativelyattached to the drive control system for the ground-engaging driveassembly; (ii) adapted to control the operation of the drive controlsystem for the ground-engaging drive assembly; (iii) operativelyattached to the load cell sensor; (iv) adapted to receive the signalindicating that the lifting column is not supporting at least thepredetermined portion of the weight of the milling machine; (v) adaptedto cause the drive control system to slow or stop the driving forceprovided by the ground-engaging drive assembly when the signal receivedfrom the sensor indicates that the lifting column is not supporting atleast the predetermined portion of the weight of the milling machine. 2.The milling machine of claim 1 wherein: (a) the drive control system forthe ground-engaging drive assembly comprises a hydraulic motor that is apart of a hydraulic circuit which includes a hydraulic fluid pump; (b)the controller is adapted to decrease the flow of hydraulic fluid to thehydraulic motor to reduce the driving force provided by theground-engaging drive assembly when the signal received from the sensorindicates that the lifting column is not supporting at least thepredetermined portion of the weight of the milling machine.
 3. Themilling machine of claim 1 wherein: (a) the drive control system for theground-engaging drive assembly comprises a hydraulic motor which isoperatively attached to a gearbox with an integrated friction brake; (b)the controller is adapted to apply the friction brake to reduce thedriving force provided by the ground-engaging drive assembly when thesignal received from the sensor indicates that the lifting column is notsupporting at least the predetermined portion of the weight of themilling machine.
 4. The milling machine of claim 1 wherein: (a) thelifting column includes an inner leg tube having a lower end to whichthe ground-engaging drive assembly is attached; (b) the outer leg tubeis adapted for axial movement with respect to the inner leg tube; (c)the linear actuator is attached at its upper end to the outer leg tubeand at its lower end to the inner leg tube, and is adapted to move theouter leg tube with respect to the inner leg tube.
 5. The millingmachine of claim 4 wherein: (a) the lifting column includes a long axis;(b) the load cell sensor is mounted to the lifting column in such amanner that it detects only forces that are directed along the long axisof the lifting column.
 6. The milling machine of claim 5 wherein theload cell sensor is substantially cylindrical and has an axis that isoriented substantially perpendicular to the long axis of the liftingcolumn.
 7. The milling machine of claim 4 wherein the load cell sensoris a pin-type load cell that attaches the upper end of the linearactuator to the outer leg tube.
 8. The milling machine of claim 7wherein the load cell sensor is spaced away from the upper surface ofthe top bracket.
 9. The milling machine of claim 8 wherein: (a) the topbracket of the outer leg tub has a pair of pin supports, each of whichincludes a hole; (b) the upper end of the linear actuator extendsthrough the top bracket of the outer leg tube and includes a hole whichis aligned with the holes in the pin supports; (c) the pin-type loadcell is placed through the holes in the pin supports of the top bracketand through the hole in the upper end of the linear actuator in order toattach the linear actuator to the outer leg tube.
 10. A milling machinefor milling a roadway surface, said milling machine having a millingmachine weight and further comprising: (a) a frame; (b) a millingassembly comprising: (i) a drum housing that is attached to the frame;(ii) a milling drum that is mounted within the milling drum housing andadapted for rotation about a substantially horizontal axis; (iii) aprimary drum drive assembly that is operatively attached to the millingdrum and adapted to rotate the milling drum; (c) a ground-engaging driveassembly that is operatively attached to a drive control system and isadapted to provide a driving force to drive the milling machine alongthe roadway surface; (d) a lifting column that is attached at its upperend to the frame and at its lower end to the ground-engaging driveassembly, said lifting column having a long axis and including: (i) alinear actuator which can be operated to raise and lower the frame ofthe machine with respect to the roadway surface; (ii) an outer leg tubewhich is fixed to the frame and which has a top bracket, said topbracket having an upper surface; (e) a load cell sensor that is adaptedto: (i) attach the upper end of the linear actuator to the outer legtube; (ii) determine if the lifting column is not supporting at least apredetermined portion of the weight of the milling machine; (iii)generate a signal indicating that the lifting column is not supportingat least the predetermined portion of the weight of the milling machine;(f) a controller that is: (i) operatively attached to the drive controlsystem for the ground-engaging drive assembly; (ii) adapted to controlthe operation of the drive control system for the ground-engaging driveassembly, including by slowing or stopping the driving force provided bythe ground-engaging drive assembly; (iii) operatively attached to theprimary drum drive assembly; (iv) adapted to control the primary drumdrive assembly, including by stopping the rotation of the milling drum;(v) operatively attached to the load cell sensor; (vi) adapted toreceive the signal indicating that the lifting column is not supportingat least the predetermined portion of the weight of the milling machine;(vii) adapted, when the signal received from the sensor indicates thatthe lifting column is not supporting at least the predetermined portionof the weight of the milling machine: (1) to cause the drive controlsystem to slow the driving force provided by the ground-engaging driveassembly; or (2) to cause the drive control system to stop the drivingforce provided by the ground-engaging drive assembly; or (3) to causethe primary drum drive assembly to stop the rotation of the millingdrum; or (4) to cause the drive control system to slow the driving forceprovided by the ground-engaging drive assembly, and to cause the primarydrum drive assembly to stop the rotation of the milling drum; or (5) tocause the drive control system to stop the driving force provided by theground-engaging drive assembly, and to cause the primary drum driveassembly to stop the rotation of the milling drum.
 11. The millingmachine of claim 10 wherein the controller is adapted, when the signalreceived from the sensor indicates that the lifting column is notsupporting at least the predetermined portion of the weight of themilling machine: (1) to cause the drive control system to slow thedriving force provided by the ground-engaging drive assembly; and in thealternative (2) to cause the drive control system to stop the drivingforce provided by the ground-engaging drive assembly; and in thealternative (3) to cause the primary drum drive assembly to stop therotation of the milling drum; and in the alternative (4) to cause thedrive control system to slow the driving force provided by theground-engaging drive assembly, and to cause the primary drum driveassembly to stop the rotation of the milling drum; and in thealternative (5) to cause the drive control system to stop the drivingforce provided by the ground-engaging drive assembly, and to cause theprimary drum drive assembly to stop the rotation of the milling drum.12. The milling machine of claim 10, wherein: (a) the controller isadapted, when the signal received from the sensor indicates that thelifting column is not supporting at least a first predetermined portionof the weight of the milling machine, to cause the drive control systemto slow or stop the driving force provided by the ground-engaging driveassembly; and (b) the controller is adapted, when the signal receivedfrom the sensor indicates that the lifting column is not supporting atleast a second predetermined portion of the weight of the millingmachine, to cause the primary drum drive assembly to stop the rotationof the milling drum; and (c) the first predetermined portion of theweight of the milling machine is different from the second predeterminedportion of the weight of the milling machine.
 13. The milling machine ofclaim 12 wherein the second predetermined portion of the weight of themilling machine is about 1200 pounds.
 14. The milling machine of claim10: (a) which includes a sensor mounting bracket that is attached to theupper surface of the top bracket of the outer leg tube; (b) wherein theload cell sensor is attached to the sensor mounting bracket in such away that the load cell sensor is spaced away from the upper surface ofthe top bracket.
 15. The milling machine of claim 14 wherein the sensormounting bracket is adapted to prevent rotation of the load cell sensor.16. The milling machine of claim 15 wherein the sensor mounting bracketis adapted to position the attached end of the load cell sensor out ofcontact with the upper surface of the top bracket by a predeterminedclearance.
 17. The milling machine of claim 10 wherein: (a) the liftingcolumn includes an inner leg tube having a lower end to which theground-engaging drive assembly is attached; (b) the outer leg tube isadapted for axial movement with respect to the inner leg tube; (c) thelinear actuator is attached at its upper end to the outer leg tube andat its lower end to the inner leg tube, and is adapted to move the outerleg tube with respect to the inner leg tube.
 18. The milling machine ofclaim 10 wherein: (a) the load cell is adapted to: (i) measure a load orstrain on the lifting column; (ii) generate a signal indicative of theload or strain measured by the load cell sensor; (b) the controller isadapted to receive the signal indicative of the load or strain measuredby the load cell sensor from the load cell sensor, said signal beingindicative of whether or not the lifting column is supporting at least apredetermined portion of the weight of the milling machine.
 19. Themilling machine of claim 18 wherein: (a) the load or strain measured bythe load cell sensor comprises an axial deformation that is a functionof the weight of the milling machine supported by the lifting column;(b) the load cell sensor is adapted to transmit to the controller acontinuous voltage signal that varies as the sensed axial deformationchanges; (c) the controller is adapted to interpret the continuousvoltage signal as indicating a decrease in the weight of the millingmachine supported by the lifting column to the predetermined portion ifthe signal from the load cell sensor falls below a predetermined voltagevalue.